1. Field of the Invention
This invention relates to a cone penetrometer which utilizes X-ray fluorescence spectroscopy to sense metals in soil or sediment samples underground.
2. Description of the Background Art
Previously, in situ analysis of soil, using a cone penetrometer, has been limited to reflectance and conventional fluorescence measurements.
U.S. Pat. No. 5,128,882 relates to a penetrometer unit which measures reflectance and fluorescence of in-situ soil. The probe is fitted with a light transparent window and a light source disposed internally of the probe. Light inside the probe passes through the window and is reflected back through the window from the soil as the probe passes through the soil. The light reflected from the soil back through the window is collected by a fiber optic link within the probe. The collected light is then transmitted through the fiber optic link to the surface for measurement and recordation of spectral distribution and intensity. Determination of the type and amount of contaminant is possible by comparison of the spectral signature of the soil to standards prepared by adding known concentrations of specific contaminant to soil similar to the soil found on the test site. It does not use
U.S. Pat. No. 5.739,536 to Frank Bucholtz et al at NRL relates to a penetrometer which uses infrared. The penetrometer has a source for providing infrared radiation which passes through the window to irradiate the soil which is adjacent to the window and a spectrometer receives and analyzes the reflected infrared radiation passing back from the soil to obtain information on chemicals present at various depths of the soil through which the penetrometer passes. It does not use X-ray fluorescence.
While x-ray fluorescence spectroscopy of soil samples has occurred on-site, the soil samples had been removed from the ground before analysis.
U.S. Pat. No. 5,014,287 relates to a relatively large portable X-ray fluorescence spectrophotometer unit that is used for environmental monitoring of inorganic pollutants. This is a commercial device which is too large to fit into a penetrometer pipe.
U.S. Pat. No. 4,510.573 relates to performing X-ray fluorescence analysis on rock samples using an instrument which is inserted via a borehole and uses a radioactive source. The device is not suitable for direct insertion in soils via a penetrometer since it is not so designed, since it contains radioactive material and since it does not have a rugged window. The device performs a mineral assay by drilling a borehole into the rock matrix, inserting into the borehole a probe containing a suitable XRF source/detector, irradiating the matrix, detecting the spectrum of radiation that is produced and analyzing this spectrum. The rugged window, which is a critical part of the present invention, is not necessary in this device. FIG. 2 shows a torpedo shaped device which is described in col. 5, lines 58-68, as having a diameter of 1.5 inches and a length of 33 inches.